This invention is related to powered conveyor rollers in which a coupling or clutch is connected between the roller shaft and the roller housing, in such a manner that if the roller housing should be held stationary by a restraining torque, the shaft can continue to rotate; and more particularly to a powered roller in which a flat spring is wrapped around the shaft in the roller housing to form a torque sensitive coupling for driving the roller. A pair of expandible bushings inside the spring form an adjustable frictional engagement between the shaft and the roller.
Powered conveyor rollers are commonly used in industry such as on a conveyor line, where certain rollers are normally driven by an axially extending shaft in the roller housing to move a workpiece along the conveyor. However, under certain circumstances, the load imposed on the roller by the workpiece, such as when the workpiece is being restrained by some exterior device, causes the roller to remain temporarily stationary, while the drive shaft continues to rotate.
Prior art related to this problem include U.S. Pat. No. 3,567,010, which issued to Hans Vom Stein on Mar. 2, 1971, discloses a roller having a load-bearing shell which when engaged by a certain load permits rotation between the roller case and the shaft.
U.S. Pat. No. 3,942,228 which issued Mar. 9, 1976, and U.S. Pat. No. 4,056,953 which issued Nov. 8, 1977 both to James L. Furlette, et al, show a driven roller in which the drive shaft has a polygonal cross-section and resilient means, either in the form of balls or a resilient tube, which cooperate to form an overload clutch.